Todd Malicoat has a write up called
The Search Marketer's
Guide to Digg, where he explains the difference between the Digg.com
editorial process and search engines editorial process. It all comes down to the
"human editorial authority," and I quote;

While most the search engines DO have human intervention - they haven't
accepted and embraced it. One of the beauties of digg is if there is CRAP in
the index - you know exactly who to blame for it.

As always, both human and algorithmic methods of intervention have their
faults. I am sure Danny will go into a bigger write up on the pros and cons of
each at a later point.

Postscript From Danny: I may write-up more on this in the future, and
I talked about it on a recent Daily SearchCast
episode. The short
story is that it's been amazing to watch Digg effectively go through the same
type of spam fighting evolution that the search engines have done.

Digg is a user driven social content website. Ok, so what the heck does that
mean? Well, everything on digg is submitted by the digg user community (that
would be you). After you submit content, other digg users read your submission
and digg what they like best. If your story rocks and receives enough diggs, it
is promoted to the front page for the millions of digg visitors to see.

The overall idea is that the community does everything. In reality, there is
a lot of backend editing and changes done by moderators. That's because the
community, if left to itself, will have a small number of people who try to
manipulate Digg for their own benefit.

PageRank performs an objective measurement of the importance of web pages by
solving an equation of more than 500 million variables and 2 billion terms.
Instead of counting direct links, PageRank interprets a link from Page A to Page
B as a vote for Page B by Page A. PageRank then assesses a page's importance by
the number of votes it receives.

Except it's far more complicated than that. Links have to be weighted, not
trusted and entire sites removed because of spam and manipulation.

Both Digg and Google (and the search engines before it) started out in what
I'd call "trusted mode," where you are optimistic that a community (people
submitting; a collection of pages) can be trusted. Along the way, they shift to
"mistrust mode" where you realize you need to be initially dubious about
everything that flows in.

If I had more time, I'd go through and do a long compare-and-contrast on how
recent Digg changes have exact counterparts in the crawler-based search engine
world. Honestly, there are times when I could do a search and replace for the
word Google to the word Digg in an article on spam fighting and the description
would be the same.

The answer, by the way, is simple. Machines that the search engines depend on
are imperfect (in particular, rankings can be manipulated more broadly), as is
the human model Digg uses (in particular, humans can miss a lot of things). The
combination of the two is much stronger. Some more thoughts on this from me: